Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $167.51   9.445%   $183.3313   $183.33   $183.35   $183.30  
  Purchase #2 $62.73   4.472%   $65.5353   $65.54   $65.55   $65.50  
  Purchase #3 $29.25   10.536%   $32.3318   $32.33   $32.35   $32.30  
  Purchase #4 $99.54   6.667%   $106.1763   $106.18   $106.20   $106.20  
  Purchase #5 $103.91   13.519%   $117.9576   $117.96   $117.95   $118.00  
  Purchase #6 $242.85   8.374%   $263.1863   $263.19   $263.20   $263.20  
  Purchase #7 $245.84   3.434%   $254.2821   $254.28   $254.30   $254.30  
  7 purchase totals = $951.63       $1,022.8007   $1,022.81   $1,022.90   $1,022.80